Polymeric materials displaying oxygen permeability are desirable for a number of applications, including medical devices. One such application is contact lenses.
Gas permeable soft contact lenses (“GPSCL”) have been made from conventional and silicone hydrogels. Conventional hydrogels have been prepared from monomeric mixtures predominantly containing hydrophilic monomers, such as 2-hydroxyethyl methacrylate (“HEMA”), N-vinyl pyrrolidone (“NVP”) and vinyl alcohol. The oxygen permeability of these conventional hydrogel materials relates to the water content of the materials, and is typically below about 20-30 barrers. For contact lenses made of the conventional hydrogel materials, that level of oxygen permeability is suitable for short-term wear of the contact lenses; however, that level of oxygen permeability may be insufficient to maintain a healthy cornea during long-term wear of contact lenses (e.g., 30 days without removal).
Silicone hydrogels (SiH's) are also currently used as materials in GPSCLs. Silicone hydrogels have typically been prepared by polymerizing mixtures containing at least one silicone-containing monomer or reactive macromer and at least one hydrophilic monomer. While this class of lens material reduces the corneal edema and hyper-vasculature associated with conventional hydrogel lenses, they can be difficult to produce because the silicone components and the hydrophilic components are incompatible. Additional material improvements to protein uptake profiles, wettability and general comfort on the eye over extended periods of time are also desirable.
Silicone elastomer contact lenses have also been made. These lenses displayed good oxygen permeability, but had poor wettability and mechanical properties. Reinforced silica filler has been disclosed as improving the physical properties of the silicone elastomers.